It seems history is repeating itself. Even in the age of the cloud, virtual data center and virtual everything, somewhere there still needs to be IT hardware that draws power and needs to be cooled. While liquid cooling has been used since the early mainframe days and is still used to cool some supercomputers, for the last few decades, air cooling became the predominant form of cooling for most IT systems as a matter of convenience.

As power demands continue to increase in the Zettabyte era, the use of liquid cooling has re-emerged, by offering effective thermal solutions for rack power densities of 25kW to 100kW per cabinet, which effectively addresses the cooling and energy challenges of high performance and hyperscale compute, as well as higher density mainstream applications.

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Droplets on a hydrophobic surface – Pixabay / doctor-a

Antiquated concept?

The thermal transfer effectiveness and energy efficiency of liquid cooling compared to air are well-known, but for most people liquid cooling may still seem like an antiquated concept. To some, there is actual fear of water, which I refer to as data center hydrophobia.

Nonetheless, more recently, many new liquid cooling technical developments and systems have entered the market which were originally aimed at hyperscale applications and are now available for conventional data center servers. Some of these systems are offered by major OEMs, such as Dell’s Triton server, while others are options for systems by HP, IBM and Lenovo.

In other cases, there are systems made by smaller manufacturers, as well as liquid cooling systems built into “standard” style IT cabinets, which can accommodate both air and liquid cooled servers in the same cabinet.

Some vendors offer hot-plug liquid cooling servers, which plug into a cabinet, making them as convenient as blade servers to swap-out server blades. This type of liquid cooled IT equipment is easier to implement for traditional facilities, and has increased interest in liquid cooling.

Know your ASHRAE

Moreover, while the industry is well aware of the ASHRAE Thermal Guidelines for air cooled IT, fewer are aware that the ASHRAE has had Liquid Cooling guidelines since 2006. In fact, the 2011 and 2015 Thermal Guidelines also includes Liquid Cooling categories W1 to W5. This should help guide facility designers and engineers, and equipment vendors and also help to reassure data center owners, operators and IT departments about utilizing liquid cooled systems.

The thermal transfer effectiveness and energy efficiency of liquid cooling are well known, but some suffer from actual fear of water

There are many myths and misconceptions about liquid cooling in the industry. To address this, The Green Grid (TGG) published the Liquid Cooling Technology Update whitepaper #70. This whitepaper provides a high-level overview of IT and facility benefits, as well as a guide to state-of-the-art liquid cooling technology. The paper defines and clarifies liquid cooling terms, system boundaries, topologies and heat transfer technologies. It is intended for chief technology officers and IT systems architects, as well as data center designers, owners and operators, which should help drive understanding and accelerate adoption.

The magnitude of demands from the expected flood of data from IoT devices, compounded by the massive bandwidth of 5G connectivity on edge data centers, will require HPC performance levels at an “industrial scale,” which will make it more difficult for air cooled IT equipment to meet density and performance requirements.

This will drive hyperscalers towards liquid cooling, which will demonstrate its effectiveness and establish its feasibility. This will validate and refine its operational practicality, as well as making it more cost effective, as volume manufacturing will lower costs to match air cooled systems.

Free cooling was first used by Google, Facebook and other “at scale” facilities, and is now commonly considered for mainstream sites. I believe that liquid cooled systems will similarly see far more widespread adoption in the not too distant future.

Julius Neudorfer is founder and CTO of North American Access Technologies. He is the author of the Green Grid’s Liquid Cooling Technology Update whitepaper #70